In the art of removing a single selected sheet from a stack of sheets, it has long been a problem to develop mechanisms for accomplishing this function which are simple in structure and which operate quickly and efficiently. The problem of withdrawing only a single sheet from a stack of sheets without removing unselected sheets is created by frictional drag between adjacent sheets, electrostatic adhesion between adjacent sheets, and the forces of inertia on adjacent unselected sheets caused by the forward movement of the selected sheet.
To overcome these problems in the past, there has been developed a number of mechanisms to insure the withdrawal of only a single sheet from the stack of sheets. Such mechanisms typically include inserting sheet-separating devices into the stack, use of air streams, joggling the stack of sheets, and various types of mechanical picker arms. However, such arrangements all have the drawbacks of being unduly complex, unreliable in operation, or too costly to employ. Moreover, most of the prior art devices relate to apparatus for withdrawing the top sheet from a stack of sheets and do not even provide means for selecting a single sheet from any level in the stack. Of course, the problems of withdrawing a sheet from an intermediate level in the stack are much more complex than merely withdrawing the top sheet from a stack of sheets. That is, the forces of electrostatic adhesion, frictional drag, and inertia tending to resist the withdrawal of only a single sheet are much greater when the sheet is being selected from an intermediate level of a stack.
Accordingly, it is an object of the present invention to provide apparatus which overcomes one or more of the aforesaid problems. Specifically, it is within the contemplation of the present invention to provide a mechanism for removing any sheet selected from a stack of sheets without removing the adjacent unselected sheets in the stack by employing a mechanism which is extremely simple in structure, reliable and efficient in operation, and inexpensive to manufacture.
It is a further object of the present invention to provide a mechanism for removing any sheet selected from a stack of sheets without removing the adjacent unselected sheets in the stack by restraining the movement of the unselected sheets, and by buckling the selected sheet so that is becomes spaced from the adjacent unselected sheets, and overcomes the forces of frictional drag, electrostatic adhesion, and inertia which tend to maintain the selected sheet in contact with the unselected sheets.